“Battery capacity” is a measure (typically in ampere hours) of the charge stored by the battery, and is determined by the mass of active material contained in the battery. The full charge capacity represents the maximum amount of energy that can be extracted from the battery under certain specified conditions. Even when the battery is new, however, the actual full charge capacity of the battery can vary from the rated (ideal) full charge capacity.
The remaining battery capacity may be expressed as a percentage of the ideal full charge capacity of the battery. This percentage value is referred to as the relative state of charge (RSOC) of the battery. Methods for measuring the remaining battery capacity may utilize the output voltage of the battery. The output voltage of the battery, however, is influenced by a variety of factors.